A variety of ionophores (ion-selective ligands) that can selectively capture a specific ion are conventionally known. Furthermore, a liquid membrane type ion-selective electrode comprising a liquid membrane type ion-sensitive membrane wherein an ionophore is supported has been developed by making use of the ionophores (patent document 1). It is possible for this liquid membrane type ion-selective electrode to detect a variety of analyte ions by changing the ionophore according to the target ion.